TV services broadcast over an IP network are referred to as IPTV. IPTV is typically broadcast using a broadband access network, in which channels are transmitted over a broadband network from a super head-end down to an end-user's set top box (STB). An example of an IPTV service is Broadcast TV, in which the most common IPTV channels, as well as additional channels with low penetration, are transmitted over a broadband network from a super head-end down to an end-user's set top box (STB). In order to minimize the bandwidth required for these transmissions it is desirable to use multicast techniques through the network.
Similarly, in mobile networks it is desirable to use broadcast/multicast delivery of Mobile TV (MTV). Multimedia Broadcast Multicast Service (MBMS) and Digital Video Broadcasting-Handheld (DVB-H) are examples of MTV broadcast technologies. A mobile telephone having an MTV client can be thought of as an equivalent to a STB in MTV implementations that receive content from a super head-end. The term “Linear TV” is used to refer to “live” ITV, which is typically delivered by broadcasting.
The same set of channels delivered over broadcast bearers may in mobile networks also be offered over dedicated unicast bearers. In this scenario, each user is allocated a dedicated channel. This is in contrast to a common bearer used in broadcast delivery over, for example, MBMS. Even though allocating a dedicated channel is less efficient from a transmission point of view, it is a pragmatic solution for many mobile networks in which broadcast delivery is not available in all geographical areas (cells). A network operator may choose to only implement MBMS in areas with high subscriber density. In some areas, MBMS has not yet been implemented, and in other areas, MBMS may never be implemented. This creates a need for delivering Linear TV over both broadcast and unicast bearers.
Furthermore, a user may start viewing an IPTV channel over an MBMS broadcast bearer, and subsequently move into an area where MBMS is not supported. In this scenario, it is necessary to switch from a broadcast delivery of Linear TV to a unicast delivery. Such a switch should be as smooth as possible and cause the least disruption to the user's viewing.
Currently there is no mechanism for switching between broadcast/multicast and unicast delivery of Linear TV.